In recent years spas have been installed by many families, reflecting a growing recognition of the healthful and soothing benefits of spa bathing. Spas are also much enjoyed in winter sport centers, such as ski resorts, where the temperature of the surrounding air may be quite cold.
The cold ambient temperature results in a considerable heat loss from the surface of the water to the air above the water. But even when the ambient temperature is warm, some heat is lost because the water in the spa is appreciably warmer than the temperature of the air.
This heat loss is an energy loss, and the desirability of minimizing the loss is apparent from the viewpoints of both energy conservation and cost. To this end, it is known in the art to provide a spa cover in the form of a sheet of stiff foamed plastic of the closed-cell type, the sheet being generally the size and shape of the exposed water surface and floating thereon.
Such a spa cover might typically be eight feet in diameter, and therefore awkward to handle and to store. To render such spa covers less awkward in handling and storage, it is known in the art to construct the spa cover so it can be folded in half.
A spa cover that folds in half gives the owner two options. Either he can remove the spa cover altogether, particularly if a large number of persons will be using the spa concurrently; or, he can fold one half over onto the other half so as to be congruent with it. This latter option probably would be chosen if only one or two persons were to use the spa. However, even in this case, the heat loss is excessive because the water surface area exposed greatly exceeds the area needed to accommodate the users. Thus there exists a need for a more efficient spa cover--one which achieves high efficiency even when the spa is being used by only one person.